SO I was just thinking aimlessly, and an idea occured to me. Aside from the fuel, a big restriction on space exploration is the problem of running out of oxygen. Why not just put a bunch of plants on the ship/station?

Trees convert CO2 into O2, right? And we convert it back, so it'd be a never ending cycle. This sounds a bit too easy, and there's got to be a reason why we haven't done this yet. So, who wants to poke holes in my theory?

Synonym

12-05-2009, 07:45 AM

It's been done out the wahzoo in SF. I assume there are limitations because of the amount of room, water, power required and that is why it isn't possible yet.

MGraybosch

12-05-2009, 07:59 AM

Why trees? Why not other plants grown hydroponically, or even cyanobacteria and algae? Also, in Hyperion by Dan Simmons, one faction made starships out of trees.

small axe

12-05-2009, 08:49 AM

The tree roots kept poking holes through the spaceship's hull? You can't grow trees in deep space because the sunlight is too weak?

I luv the classic sf movie SILENT RUNNING with its huge deepspace greenhouses. I luv the movie THE FOUNTAIN with its Tree of Knowledge in space.

Whatever problem they had in the BIODOME projects a few years ago may be your issue. It was supposed to be a totally self-contained, re-cycled, perfectly self-sustaining environment ... but it broke down, I think.

I forget what went wrong. You might research that though.

I think someone passed gas and ka-boom, it was like a row of dominoes going down.

One scientist oinks from the wrong end and all the sequoia trees die in outer space!

Thomas_Anderson

12-05-2009, 08:57 AM

Roots can be cut and sunlight can be synthesized.

Xelebes

12-05-2009, 09:09 AM

Trees produce marginal oxygen surpluses because they consume oxygen during the night. You want blue algae.

benbradley

12-05-2009, 09:09 AM

SO I was just thinking aimlessly, and an idea occured to me. Aside from the fuel, a big restriction on space exploration is the problem of running out of oxygen. Why not just put a bunch of plants on the ship/station?

Trees convert CO2 into O2, right? And we convert it back, so it'd be a never ending cycle. This sounds a bit too easy, and there's got to be a reason why we haven't done this yet. So, who wants to poke holes in my theory?
It's no doubt possible (not neccesarily with trees which are probably to big to grow in any current craft in space, but with other plants), but it doesn't appear to be practical yet. Even in the International Space Station, they take up supplies every few months, either in a Space Shuttle or a Soyuz capsule. I can imagine a not-much-larger station for people in space would have enough "space" inside to grow its own plants, both for food and to create oxygen. Such a station would be much closer to self-sustaining than the current ISS. But I haven't heard of any such thing, even on the drawing board. Maybe there's something to go along with this new "Orion" thing NASA is building.

Even if they are only marginally useful, though, it wouldn't surprise me if they became popular simply because people liked them.

You can wave around scientific papers showing how pot plants in an office don't actually help the atmosphere, but people still keep them because they like the look and feel of them.

Another point - once something becomes rarer and harder to do, it also becomes more valuable. So rich companies would start growing complete trees in the public areas of their spaceships just because it is hard - it would be a luxury item - just like rich companies now have ridiculously expensive artworks and carpet in their foyers for no apparent reason.

So I think once you start having a reasonably large area, people will start growing trees - whether it makes scientific sense or not.

Mac
(PS: Remember, too, that 'space' in a space-station might be reasonably cheap. Simply inflate a plastic bubble, spray it with a shell of epoxy and you've got the basics. You would put a wall of storage compartments on the outside as a bit of a radiation barrier, but it wouldn't be that much more expensive. Remember, making an area bigger in volume is reasonably cheap. The material costs goes up by the square of the size, but the volume goes up by the cube of the size)

efkelley

12-05-2009, 11:31 AM

Did you need trees in your WIP? Because I'd take a good old CO2 Scrubber any day over that. Just make the things hyper-efficient and you don't need to worry about running out of oxygen anytime soon.

BigWords

12-05-2009, 11:27 PM

If trees are out of the question, how about some kind of plankton in the water supply which produces oxygen, perhaps?

MGraybosch

12-05-2009, 11:35 PM

If trees are out of the question, how about some kind of plankton in the water supply which produces oxygen, perhaps?

Like I said: algae and cyanobacteria. Just keep it out of the drinking water.

small axe

12-06-2009, 09:12 AM

Roots can be cut and sunlight can be synthesized.

The incessant tapping of the woodpeckers would drive the astronauts mad. :)

But seriously: the BioDome 2 project was designed to be just such a closed system, so whatever failed with that might be your key issue? I think it had greenhouses but I don't know about trees.

jhmcmullen

12-08-2009, 08:54 PM

There are still problems with producing a closed system like that, but the idea has been around for a while. If you look at some of the plans for space habitats from the late seventies, early eighties, oxygen was often meant to be produced by plants. (Someone had not done the calculations on this, preferring to depict habitats as being like southern California, but the idea is fairly sound.) Figuring out what plants and how many there are and how many animals will be respiring and what the light source is...well, that part is tough. Making oxygen production equal oxygen consumption in a way that leaves you with the right oxygen level in the atmosphere and everyone (and everything) alive is hard.

Mr Flibble

12-08-2009, 08:57 PM

his sounds a bit too easy, and there's got to be a reason why we haven't done this yet.

When I took a trip to NASA two years ago they had a mock up of the base they want to have on the moon ( in prep for the one they want to put on Mars).

Lots of plants ( not trees, sorry) grown hydroponically to help out with oxygen. So they are doing / planning on doing it. Can't remember the details I'm afraid - my son dragged my off to look at the robotic probes...

benbradley

12-08-2009, 09:45 PM

The tree roots kept poking holes through the spaceship's hull? You can't grow trees in deep space because the sunlight is too weak?

Roots can be cut and sunlight can be synthesized.
The Sunlight in space is as strong as on Earth's surface, and a lot stronger in some areas such as UV. The windows may need filters to keep the UV out.

The incessant tapping of the woodpeckers would drive the astronauts mad. :)

But seriously: the BioDome 2 project was designed to be just such a closed system, so whatever failed with that might be your key issue? I think it had greenhouses but I don't know about trees.
It looks like you mean BioSphere 2 (http://en.wikipedia.org/wiki/Biosphere_2). They lost oxygen, I read it was being absorbed by the concrete structure.

There are still problems with producing a closed system like that, but the idea has been around for a while. If you look at some of the plans for space habitats from the late seventies, early eighties, oxygen was often meant to be produced by plants. (Someone had not done the calculations on this, preferring to depict habitats as being like southern California, but the idea is fairly sound.) Figuring out what plants and how many there are and how many animals will be respiring and what the light source is...well, that part is tough. Making oxygen production equal oxygen consumption in a way that leaves you with the right oxygen level in the atmosphere and everyone (and everything) alive is hard.
O'Neil's "The High Frontier" described large colonies. I've got an earlier printing with the original cover. It's shown here, but the pic doesn't do it justice:
http://en.wikipedia.org/wiki/The_High_Frontier:_Human_Colonies_in_Space
It's a cylinder (rotating to make gravity) with a small city, trees and farmland on the inner surface.

small axe

12-09-2009, 02:18 AM

It looks like you mean BioSphere 2 (http://en.wikipedia.org/wiki/Biosphere_2). They lost oxygen, I read it was being absorbed by the concrete structure.

You're right ... I must've been thinking of
"Mad Max's Beyond THUNDER Dome!"

And that would be a bad design for a sustainable environment, since we'll recall that the law of ThunderDome is:

"Two men enter, one man leave!" :)

Good Lord: the spaceship lands, and the trees are all fine ... but the crew had to eat each other to survive!

efkelley

12-09-2009, 05:00 AM

Good Lord: the spaceship lands, and the trees are all fine ... but the crew had to eat each other to survive!

Plan B in most cases.

Which should serve as a warning to anyone visiting my house.

Lhun

12-10-2009, 09:05 PM

It looks like you mean BioSphere 2 (http://en.wikipedia.org/wiki/Biosphere_2). They lost oxygen, I read it was being absorbed by the concrete structure.The big difference between a project such as BioSphere and a spaceship is that the spaceship just needs a design that makes it self-sufficient somehow. The goal isn't to have a completely self-sustained biological microcosmos.
Point in case: recycling oxygen and water (as well as other simple chemicals) is trivially easy, and not very costly energy-wise. So, there's no problem with using solar power and a technological solution to getting oxygen, instead of creating a whole biosphere. Plants would mostly be grown for food (or decoration) not for oxygen.

Sarpedon

12-10-2009, 09:32 PM

They lost oxygen, I read it was being absorbed by the concrete structure.

Yup, concrete absorbs water and oxygen in the curing process, which continues long after its 'solid.' They didn't factor that in? Hahaha.

And wouldn't a large plant like a tree require gravity for its internal processes? Or would capillary action alone be enough for its circulation? I seem to recall that phloem tissues rely on gravity to transfer nutrients back down to the roots. Maybe I'm wrong.

And how would the tree know which way to grow? Doesn't gravity factor into that as well?

mercs

12-10-2009, 09:58 PM

I'm amazed they never featured a bio-deck in star trek for example. Somewhere where this could be mentioned. It wouldn't have a widescale use as trees don't produce anywhere near enough oxygen to justify the vast space required, but could reduce marginally the overall supply...

efkelley

12-11-2009, 12:10 AM

I'm amazed they never featured a bio-deck in star trek for example. Somewhere where this could be mentioned. It wouldn't have a widescale use as trees don't produce anywhere near enough oxygen to justify the vast space required, but could reduce marginally the overall supply...

They make mentions of arboretums more than once, although I believe Next Generation was the only series to actually place scenes there.

In another aside, the title of this thread is the title of the next Samuel L. Jackson movie. Or rather should be. ;-)

Liosse de Velishaf

12-11-2009, 01:08 AM

You're right ... I must've been thinking of
"Mad Max's Beyond THUNDER Dome!"

And that would be a bad design for a sustainable environment, since we'll recall that the law of ThunderDome is:

"Two men enter, one man leave!" :)

Good Lord: the spaceship lands, and the trees are all fine ... but the crew had to eat each other to survive!

Several space video games use the term "biodome". It's not like you invented a new term. You probably heard it somewhere and got confused. Happens to me all the time.

Pthom

12-11-2009, 01:47 AM

...there's no problem with using solar power and a technological solution to getting oxygen...
Indeed. In fact, at the distance Earth is to the Sun, a space habitat will likely have more problem getting rid of excess energy than running out of it.

BigWords

12-11-2009, 02:16 AM

Indeed. In fact, at the distance Earth is to the Sun, a space habitat will likely have more problem getting rid of excess energy than running out of it.

Just think... You could play computer games all day long and not have to worry about the power cutting out. I could actually think of ways to use up that much excess energy, and I wouldn't have to worry about annoying Friends Of The Earth types bitching at me about having my Xbox360, PS3, DVD player, Freeview box, computer, laptop and radio all running pretty much constantly.

small axe

12-11-2009, 04:04 AM

The Sunlight in space is as strong as on Earth's surface, and a lot stronger in some areas such as UV.

Okay, I admit, I'm utterly in need of help on that one: How can there be enough sunlight farther away from the Sun to grow trees?

Do you just mean, at the same distance from the Sun, outer space and earth get as much sunlight?
(Because admittedly I was just picturing spaceships traveling out into deeper space, growing trees for breathing air ... )

I thought the main reason the outer planets are cold is because of their distance from the Sun, the energy of light falling off at ... well, I'm ignorant of that equation too without looking it up, but it falls off FAST.

Heck, my Grandma used to say if you tilt your gardens towards the Sun, the angle that sunlight hits the ground can vastly inhance the amount of growing rays available to plants; a garden tilted up a few degrees in Indiana lets as much sunlight hit them as if they were growing in Florida etc.

benbradley

12-11-2009, 04:29 AM

Okay, I admit, I'm utterly in need of help on that one: How can there be enough sunlight farther away from the Sun to grow trees?

Do you just mean, at the same distance from the Sun, outer space and earth get as much sunlight?
Yes, exactly. The Sun is a bit brighter in space, because it doesn't have to go through the Earth's atmosphere. And especially in ultraviolet light it's brighter, because the atmosphere substantially reduces UV.

I was assuming this spaceship would be in low Earth orbit or "nearby" as in a Lagrange point between the Earth and Moon.

(Because admittedly I was just picturing spaceships traveling out into deeper space, growing trees for breathing air ... )

I thought the main reason the outer planets are cold is because of their distance from the Sun, the energy of light falling off at ... well, I'm ignorant of that equation too without looking it up, but it falls off FAST.
Yes indeed. That's called the "inverse square law." As you double the distance from a point-source of light (which the Sun at the distance from the Earth is a close enough approximation), the rays spread out so it takes four times the area to capture the same rays. Take the distance ratio, square it, and take the reciprocal of that, and you get the amount of sunlight at the new distance. For three times the distance between the Sun and the Earth you get 1/9th the amount of light per unit area.

Here's a description:
http://en.wikipedia.org/wiki/Inverse-square_law

Heck, my Grandma used to say if you tilt your gardens towards the Sun, the angle that sunlight hits the ground can vastly inhance the amount of growing rays available to plants; a garden tilted up a few degrees in Indiana lets as much sunlight hit them as if they were growing in Florida etc.
Yeah. that's the same (pretty much) as tilting solar panels so they always directly face the Sun. But again, because sunlight at an angle goes through more atmosphere than when it's straight overhead, there's a little less light, especially in the ultraviolet. There's a lot more absorption at sunrise and sunset because of how much air the light goes through, making the Sun look more orange-colored at those times.

Pthom

12-11-2009, 04:32 AM

A great deal of solar radiation (including, but not limited to the visible spectrum) is absorbed by Earth's atmosphere. More is reflected back into space (by snow, clouds, water, white rooftops, etc.)

Put an orbital arboretum in, say, lunar orbit (the Earth/moon L4 or L5 point will suffice). Except when eclipsed by Earth itself, the contents of this arboretum will fairly cook (think microwave) unless something is done to insulate them from the radiation.

There is this deal about the inverse square law, right? Where the intensity of radiation emitted from a point source (the sun is close enough to one of those) diminishes by the square of the distance. Go twice as far from the sun as Earth is, and the radiation reaching you is only 1/4 as much.
But...

it
is
still
a
lot.Plenty enough to keep plants alive.

small axe

12-11-2009, 05:59 AM

Thanks for the explanations! I was just making sure it wasn't some issue of outer space being so full of radiation or the accumulated light of a billion stars etc being enough to grow trees (which is a cool thought in its own right)

I know I've read how atmosphereless space leaves Mars-bound crews open to weird radiations, solar flares etc but didn't know how high those radiations were all the time.

BillPatt

12-11-2009, 12:20 PM

I think you are forgetting something along the way. Yes, you want to split off CO2 and get the O2 back. But what about the carbon? It's locked away in the tree. You actually need that carbon to make carbohydrates and such for the algaeburger for lunch. That's why most of the time, the 'hydroponics bay' is really the place where they use food plants for air regeneration. It'ss done in tanks of algae where the air is bubbled through. Trays of vegetables supplement this food source, as well.

If you are going to go into the whole recycling works discussion, a tree would only be used as a carbon sink, as well as a social setting. Poul Anderson's Harvest of Stars has a gigantic redwood in a habitat at L-5, and it's in a park all by itself.